Technical Abstract:
Development of the ethanol industry in the southeastern U.S. is limited by the availability of corn and other feedstocks produced in the region. Viability of a plant will require additional feedstocks to supplement locally-grown corn. These studies were conducted to evaluate the biological and economic feasibility of using pearl millet as a supplemental feedstock in a dry-grind ethanol production process. For fermentation analysis, pearl millet grain was subjected to different grinding processes. The rates of the fermentation process for the pearl millet treatments and a corn control were measured, and the resulting composition of the distiller’s dry grains with solubles (DDGS) was determined. A process and cost analysis was used to assess the economic feasibility of using pearl millet as a feedstock. Expected yield of ethanol and DDGS was calculated based upon grain composition. Other variables in the model include the cost of feedstock, sizing of equipment, utility consumption, operating costs, capital costs, and revenue from the ethanol and DDGS. Fermentation studies demonstrated that pearl millet can be converted to fuel ethanol using a conventional dry-grind corn-to-ethanol process without significant modifications. Final fermentation efficiency was approximately 4% less than corn, but pearl millet fermented more quickly and reached 85% fermentation approximately 12 hours earlier than the corn treatment. The pearl millet DDGS was higher in protein and fat, and lower in fiber compared to corn DDGS. The process and cost analysis indicated that the higher protein content of pearl millet would result in a 13% greater DDGS coproduct income compared to corn. Within the limitations of this preliminary analysis, results suggest that even with a 10% premium on the cost of pearl millet, the net cost of ethanol production is $0.06 per gallon less than production using corn. Other potential value not accounted for in the process and cost analysis include lower electricity requirements to grind pearl millet, and faster batch processing due to the faster fermentation rates. Biologically and economically, pearl millet is a feasible supplemental feedstock for dry-grind ethanol facilities in the southeastern U.S. Regionally grown pearl millet should benefit rural economies in the southeast that are planning to import feedstock for ethanol production.